dizwiz24

I want to post this as a follow-up to this post:


http://forums.corvetteforum.com/c4-f...s-cam-lt1.html

Since that post, I have added the following mods to my 93 lt1 6spd:

-AFR 195 LT4 eliminator comp ported, 61cc heads (lowers compression from 10.5:1 stock to 9.6:1). HD 155 lb springs.

-Lloyd Elliot 224/236 .575/.582 (w/ 1.6:1 roll rockers) 114 LSA cam in place of hotcam

-extra booster fuel pump (always running) fed by walbo 255 l/hr in tank pump that I had in there before (w/ racetronix harness).

-LT4 extreme duty timing chain

-2.75" 8 rib pulley (from blowerworks) in place of 3" 8 rib pulley (bigger idler pulleys, etc. needed added to take up the slack). This has always been on a special, dedicated drive bracket that Greg@ blowerworks made for me and my p600b.

-LT1 intake ported by Lloyd Elliot.

- Gen II optispark in place of vented Gen 1 optispark.

I made 485 STD rwhp / 473 rwTQ on a 95F day vs. 469 rwhp / 462 rwTQ on an 82F day.

I expected I would make more power than this (I expected 530 rwhp), however theres 2 important factors:

1. I didnt rev higher than 5400 RPM, the car was still making power when I cut it off. I am afraid of taking it beyond 5500 rpm with my stock bottom end. Maybe it would be ok to 6000 rpm? I dont know. Also, Im making 10 psi boost at 5000 rpm, and would be making (in theory) 12.5 psi boost at 6000 RPM. Thats a lot of boost.

2. the hot day. Even with STD corrections, I still think Id pick up power on a cooler day.

Finally, one important thing is that I didnt appear to give much up in terms of low end grunt. This was a big risk with lowering compression ratio, putting on bigger cc heads, and a slightly bigger camshaft.

BTW: I tried advancing timing from 22 degrees to 24 degrees and I got 8 degrees knock retard at 5000 RPM. So I set it back to 22 degrees.
Spark timing starts off around 32 degrees (peak) at 2800 RPM and gradually drops down to 22 degrees from 4500 RPM to redline.



Heres the charts:

Chart A: 4th run showing 485 rwhp


Chart B: 4th run AFR and HP/TQ info by RPM


Chart C: Before and After the above named mods were added


Its a real blast to drive on the street and certainly feels faster than before. I need to get it to the dragstrip

Im sure I'll get 500+ rwHP with the right air and bravery (willing to rev a little higher)

tequilaboy

Thanks for posting.

Interesing results (and quite similar to mine when considering the correction factor differences between STD and SAE). You will likely pick up a few more HP if you're willing to rev to 6,000 rpm or beyond, but of course this is a bit risky with stock internals.

Found this article with a decent description of the differences between STD and SAE correction factors including examples.

http://www.gmhightechperformance.com...wer/index.html

For comparison, My recent numbers were 478 rwhp and 465 rwtq (SAE) with intercooled Powerdyne BD-11A, 9 psi peak boost @ 6500 rpm (stock L98 7.2" crank and 3.12" blower pulley). Same 3.05 internal step-up ratio as P-600B. Our hp and torque curves vs rpm are also quite similar, but I revved to 6,500 rpm but with forged rods and pistons.

As ususal there is more than one way to skin a cat.

Its unfortunate that the head swap did not result in significant gains, but again, this is similar to my own experience.

Now where do we go from here? I'm thinking a bigger blower is in order.

bogor

David,
I noticed you are running the same meth/water injection as me. Have you tried a smaller nozzle? I started with a 16GPH nozzle and 100% water and now use a 9 or 10 GPH nozzle and 50/50 mix of ethanol/water. No dyno but it definitely feels like it picked up power (currently Spark advance around 20' at 10 psi @5500 and CR at 9).

dizwiz24

bogor,

nozzle part says its a N-15, so I assume thats 15 gallon/hr.

Ive always run 50/50 meth/water (actually its 49 meth/51 water...I use Snow performance 'Boost Juice' as pure methanol is hard to get thanks to drug addicts making drugs w/ it aroudn here).

Are you sure that your performance improvement is not from the smaller nozzle, but from the 50% methanol (vs. 0% methanol)?

Ive heard a lot of people get performance improvement with 100% methanol. In fact, most import guys I talk to (ex. Mitsubishi evo) use 100% methanol.

bogor

As I understand it meth will increase octane And water will prevent pre ignition by its cooling effect so an increase in power will be possible to achieve due to less risk of detonation (same end result but two different mechanism) I did only minor changes in spark advance and was running same boost (no detonation observed) so I suspect large amount of water cool the intake charge and cylinder too much (resulting in loss of power). Finding meth here is difficut so Im actually using ethanol but should not be of any major importance. Will prob know more after next Tuesday when I will dyno the car for the first time ever.

Boosted LT4

Haven't heard from Dizwiz24 in a while. Still have this car? How has it been holding up?
Update?

Thanks

dizwiz24

yes, im here;

Definitely still have the car.

This dyno chart is not my most recent set of results. I ran again 2 months later and discovered that lowering my timing down low picked up low end TQ (and it wasnt due to knock retard activity).

Held up fine. I ran into one hitch this past summer... I installed 'solid motor mounts' made by user 'churchkey'. Theres really very minimal vibration penalty, and thats at idle. If you have stuff in your glovebox, then yeah, theres rattle. But remove the stuff and all noise is gone.

Anyways..... the 'rattle' was shaking loose my Moates adapter from the PCM socket.

Every time Id hook and accelerate, max g-force (usually 1st gear, when I had traction), the engine would suddenly die, and then come back to life once the g-forces settled down.

Here I thought I had a bad ground and I sidelined the car for 6 weeks redoing grounds, battery connections, replacing wires that looked 'brittle, old', re-crimping connections, etc,

Come to find out it was my Moates adapter jiggling loose out of the socket.

I did not get time to do another set of dyno pulls. The biggest issue (as you see from my above graphs), was I did not take it above 5400 RPM because I ran out of time on the dyno before the next appointment.

I now have AFR 1 7/8" stepped headers with 3" exhaust and x-pipe. Perhaps I will see some gain up top ? (and hopefully not much lost down low)...this is vs. 1 3/4" TPIS headers and the stock lt1 exhaust...

Anyways, this past summer I moved and was real busy with it. I did drive the car around (including some 4 hour trips), but didnt hit any tracks with it (regrettably).